检索结果-内蒙古大学图书馆

Risk-based study on under voltage load shedding schemes

Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2006年第19期26卷 18-22页

作者： Dai, Jian-Feng Zhu, Ling-Zhi Zhou, Shuang-Xi Lu, Zong-Xiang State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

A risk based method is proposed to design under voltage load shedding (UVLS) scheme. Different with traditional methods, the proposed one employs a series of risk indices, which are obtained based on a full-scale contingencies analysis, to determine the operating parameters of load shedding. According to this method, the load bus, in which the UVLS can exert itself with the highest efficiency to prevent voltage collapse, is selected as the first candidate to execute load shedding. And the amount of loads to be shed is identified though a relationship between risk values and shedding amount. The selection of shedding time conforms to the principle that the compound risk brought by failed shedding and unexpected shedding must be the minimum. Experiments conducted for IEEE 39-bus system reveal that the proposed method redound to identify the location, amount and time of load shedding more accurately and reasonably due to taking into account a great deal of uncertain factors.

关键词： Electric load shedding

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Study on probability of voltage instability based on the stochastic characteristic of load margin index

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2006年第13期26卷 26-30页

作者： Dai, Jian-Feng Wang, Hai-Chao Zhou, Shuang-Xi Lu, Zong-Xiang Zhu, Ling-Zhi State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

In order to make up the deficiency of traditional analytical method used in the research of voltage stability problem, we need to know the probability information concerned with voltage instability. Therefore, this paper proposes a method to calculate the probability of voltage instability based on the stochastic characteristic of load margin index. This method firstly determines the stochastic characteristic of load margin index through an analysis about the randomicity of parameters which tie up with the tracing of critical point in continue power flow computation, and then figures out the probability of voltage instability by using moment and cumulate method. Owing to take into account more uncertain factors' influence on the voltage stability, the result acquired by this method is much more accurate and reasonable. A numerical simulation based on IEEE 39-bus system reveals that the proposed method works properly.

关键词： Electric power systems

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Progressively Converging Deadbeat control for UPS Inverter

Progressively Converging Deadbeat Control for UPS Inverter

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Annual IEEE Conference on Applied power Electronics Conference and Exposition (APEC)

作者： Y.D. Liu Y. Xing L.P. Huang M. Sakane State Key Laboratory of Security Control & Simulation of Power Systems and Large Scale Generation Equipments Department of Electrical Engineering Tsinghua University Beijing China College of Automation Engineering Nanjing University of Aeronautics and Astronautics Jiangsu China GS Yuasa Power Electronics Limited Osaka Japan

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Improved simultaneous extrapolation in sharp impulse signals in time and frequency domains

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2006年第18期26卷 133-137页

作者： Zou, Jun Guo, Jian He, Jin-Liang Zhang, Bo Teng, Wen-Rui State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing 100084 China Dept. of Electrical Engineering Henan University of Technology Zhengzhou 450042 China

The characteristic of the transient response of the grounding system takes on a fast rising and slow damping with the lightning excitation. An improved simultaneous time and frequency domain extrapolation method is presented based on Hermite function expansion, which takes the above mentioned characteristic of the transient signal into account, using early time response and low-frequency data, the complete electromagnetic response is generated. By using mutually complementary data, simultaneous extrapolation in time and frequency domains are carried out by using the Hermite polynomials as the basis function. However, the extrapolation method is not suitable to deal with the transient response with the fast pulse excitation. The improvement for the extrapolation method is to pre- and post-process the transient response data with the fast pulse excitation. As a pre-processed procedure, in order to reduce the condition number of the matrix used for determined the coefficient of basis function, the scale transformation is used in time and frequency domain respectively, and the data in time domain is smoothed and padded with zero. An adaptive algorithm to determine the order of Hermite function is also proposed. As a post-processed step, the transient data are smoothed by using GPOF to obtain a convergent result. The numerical example and the field measurement are presented to illustrate the application of this methodology. The method proposed enhances the ability of the simultaneous time and frequency extrapolation techniques.

关键词： Signal processing

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Adaptive Galerkin approach of the indirect boundary element method for calculating 3D linear magnetostatic field

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2006年第1期26卷 96-100页

作者： Zou, Jun He, Jin-Liang Yu, Hai-Yu Teng, Wen-Rui State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing 100084 China Dept. of Electrical Engineering Henan University of Technology Zhengzhou 450042 China

The indirect boundary element method has some special advantages for the 3D linear magnetostatic field calculation by using the equivalent magnetic surface charge. In order to improve the accuracy of solutions and decrease the computational costs, an adaptive Galerkin approach to solve the magnetostatic integral equation is presented by using the h-type refinement technology. The basic idea of the proposed approach can be summarized as follows. The error of magnetic flux density is globally minimized in the Galerkin sense in the implementation, so the continuity error of magnetic flux density of each element can be served as a criterion to guide the adaptive refinement. The singularity of geometric corners and edges can be overcome due to the scheme of the discretization of the integral equation with Galerkin's approach. In addition, a local resolution technology is proposed, which leads to the minimal refined unknown. The numerical examples show the proposed method is efficient and accurate by comparison to the analytical solutions and the measured results.

关键词： Magnetic fields

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Calculation on the thermal field of the water cooling stator of three-gorge hydro-generator

Calculation on the thermal field of the water cooling stator...

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ICEMS 2005: 8th International Conference on Electrical Machines nd systems

作者： Wang, H.Y. Su, P.S. Wang, X.H. Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing 10084 China

ISBN: (纸本)7506274078

To simplify the calculation of winding bar temperature for the condition monitoring of the water cooling stator of Three-Gorge Hydro-Generator, this paper calculates three of two-dimension thermal fields. Using the three fields simulates the different section along the axial direction of the generator. The total amount of heat taken away by water can be calculated by weighting the result of three fields on the total axial length of them. Four groups of thermal-fields with different outlet-water temperature are calculated by using ANSYS multi-physical software. The calculation results of temperature of measurement-point between up-layer and down-layer bars in stator are partly supported by the measurement data. And the relatively error between the heat taken by cooling-water and the heat generated by the stator bar is always less than 5%.

关键词： Stators

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Optimized design of main protection configuration scheme for internal faults of shawan generator

Optimized design of main protection configuration scheme for...

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ICEMS 2005: 8th International Conference on Electrical Machines nd systems

作者： Sun, Yuguang Wang, Xiangheng Gui, Lin Wang, Weijian Department of Electrical Engineering State Key Laboratory of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing 100084 China

ISBN: (纸本)7506274078

In order to provide high-quality protection for large- and medium-sized generators, a new feasible method of designing main protection configuration scheme for internal faults of generators is desirable. Based on calculation of all the possible internal faults with the multi-loop method, the optimized design method is illustrated through Shawan generator in this paper. With this method, the optimal protection configuration scheme, composed of the split-phase transverse differential protection, two sets of incomplete longitudinal differential protection as well as one set of single element transverse differential protection, is determined for the internal faults of Shawan generator, which has two branches in each phase. The rate of operation and double-protection of the optimal scheme both reach the maximum. In addition to that, on all the possible phase-to-phase faults, at least two kinds of protection of the optimal scheme are sure to operate correctly. The optimized scheme excels the conventional one in protection performance index, which verifies the validity of the optimized method of designing main protection configuration scheme for generators.

关键词： Electric generators

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Research on the prediction-model of the surface-temperature of large oil-immersed power transformer

Research on the prediction-model of the surface-temperature ...

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ICEMS 2005: 8th International Conference on Electrical Machines nd systems

ISBN: (纸本)7506274078

In order to detect the abnormal temperature of large oil-Immersed power transformer earlier, this paper presents a new prediction-model of surface-temperature for the transformer to predict the normal surf ace-temperature. And to compare the difference between the predicted value and the measured value can judge If the condition of the transformer Is fit to operate. The model parameters are estimated from the field data by using the Partial-Least-Square method, which overcomes the instability of results estimated by using the traditional Least-Square method. Furthermore, the appropriate amount of data for the parameter estimation was decided according to the principle of Heat Transfer and the characteristics of the predicted deviation, such as mean, variance and normal distribution. The prediction model is verified from the accuracy of results predicted with one year of field data.

关键词： Electric transformers

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Reinforcement learning control for ship steering using recursive least-squares algorithm

Reinforcement learning control for ship steering using recur...

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作者： Shen, Zhi-Peng Guo, Chen Yuan, Shi-Chun Lab. of Simulation and Control of Navigation Systems Dalian Maritime Univ. Dalian 116026 China State Key Laboratory of Intelligent Technology and System Tsinghua University Beijing 100084 China

ISBN: (纸本)008045108X

Recursive least-squares temporal difference algorithm (RLS-TD) is deduced, which can use data more efficiently with fast convergence and less computational burden. Reinforcement learning based on recursive least-squares methods is applied to ship steering control, as provides an efficient way for the improvement of ship steering control performance. It removes the defect that the conventional intelligent algorithm learning must be provided with some sample data. The parameters of controller are on-line learned and adjusted. simulation results show that the ship course can be properly controlled in case of the disturbances of wave, wind, current. It is demonstrated that the proposed algorithm is a promising alternative to conventional autopilots. Copyright © 2005 IFAC.

关键词： Learning algorithms

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power losses for IGCTs and diodes in MV three-level inverters

Power losses for IGCTs and diodes in MV three-level inverter...

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Sixth International Conference on power Electronics and Drive systems, PEDS 200

作者： Yuan, Liqiang Zhao, Zhengming Yang, Zhi Dept. of Electrical Engineering Tsinghua Univ. State Key Lab of Control and Simulation of Power System Beijing China Dept. of Frequency-converter and Control System GuoDian NanJing Automation Co. Ltd. Nanjing China

ISBN: (纸本)0780392965

The power-loss models for different switching states of IGCTs and diodes in MV (medium voltage) three-level NPC (neutral point clamped) inverters are presented in this paper. The models, simulation implementation and the revisional experiments on IGCT test platform are described in details. The relation between the power losses and the other elements of the inverter is analyzed and discussed. © 2005 IEEE.

关键词： Electric inverters

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