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Two-stage heuristic-correction for dynamic reactive power optimization based on relaxation-MPEC and MIQP

Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2014年第13期34卷 2100-2107页

作者： Ding, Tao Guo, Qinglai Bo, Rui Sun, Hongbin Wu, Wenchuan Zhang, Boming Yao, Zhengyi State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Haidian District Beijing 100084 China Midwest ISO St. Paul 55108 United States Baoji Power Supply Bureau Baoji 721004 Shannxi Province China

To achieve a fast approach to the dynamic reactive power optimization model, a mixed integer nonlinear programming model was set up, with consideration of the discrete reactive power equipment operation limit and power grid security constraints, to minimize the transmission losses. Furthermore, a method called heuristic search and variable correction was proposed that for the first stage, the discrete variables are relaxed into continuous ones, which leads to an optimization model with equilibrium constraints. According to the optimal value of relaxed model, a mixed integer quadratic programming model is formulated to minimize the objective of approximation variance, satisfied the discrete switching operation constraints in primary model. For the second stage, the continuous variables are redressed with respect to the determined discrete variables. The impact of adjustment step and operation limit on the optimal solution was fully studied in IEEE 14-bus test syst.m. Besides, the result of IEEE 30, 57, 118 test syst.ms show that an optimal solution can fast be obtained by proposed method, and the precision satisfies the actual engineering, which can also employ the parallel technology. © 2014 Chinese Society for Electrical Engineering.

关键词： Integer programming

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Frequency dependent network equivalent based electromagnetic and electromechanical decoupled hybrid simulation

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2012年第16期32卷 107-114页

作者： Zhang, Yi Wu, Wenchuan Zhang, Boming Gole, Aniruddha M. State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Haidian District Beijing 100084 China Department of Electrical and Computer Engineering University of Manitoba Winnipeg R3T 5V6 Canada

Neither electromechanical transient stability analysis (TSA) program nor electromagnetic transient (EMT) programs can be used individually for the transient stability studies of the large scale AC/DC syst.ms. This paper presented an electromagnetic and electromechanical hybrid simulation syst.m, based on a frequency dependent network equivalent. Firstly, the framework and the main modules of the proposed hybrid simulation syst.m were introduced. Secondly, the methods to calculate the equivalents of the electromagnetic side and the electromechanical side were introduced. The discussion on the difference between the traditional method and frequency dependent network equivalent (FDNE) and the flowchart of the hybrid simulation were also given. In the last part of the paper, AC syst.m and AC-DC hybrid syst.m are both used as examples to demonstrate the accuracy of the proposed hybrid simulation syst.m's simulation results. © 2012 Chinese Society for Electrical Engineering.

关键词： Hybrid syst.ms

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Novel active damping control scheme for a three-phase active rectifier with LCL-filter

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Diangong Jishu Xuebao/Transactions of China Electrotechnical Society 2008年第9期23卷 86-91页

作者： Huang, Yuqi Jiang, Xinjian Qiu, Arui State Key Lab. of Security Control and Simulation of Power Systems and Large Generation Equipments Tsinghua University Beijing 100084 China

A novel active damping control scheme is developed to eliminate stability problems arisen in the current control of a three-phase voltage source active rectifier (VSR) with LCL-filter. A converter side inductance voltage feedback loop is introduced in the traditional voltage oriented control to stabilize VSR. A simplified discrete model including the current control loop and LCL-filter is established with one sample delay, considering time delays induced by S/H (sampling and holding), processing and modulation. The amplification coefficient of the converter side inductance voltage feedback loop is tuned up to change the unstable poles of LCL-filter. Parameter estimate methods are used to remove unnecessary sensors. simulation and experiment of VSR with LCL-filter demonstrate the proposed active damping control scheme and the stability analyses.

关键词： Inductance

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Risk-based study on under voltage load shedding schemes

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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 syst.m 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 syst.m reveals that the proposed method works properly.

关键词： Electric power syst.ms

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Air-gap magnetic field distribution and inductance characteristics in a long primary sectional powered variable pole pitch linear induction motor

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Qinghua Daxue Xuebao/Journal of Tsinghua University 2014年第9期54卷 1161-1165and1172页

作者： Mu, Shujun Chai, Jianyun Sun, Xudong Wang, Shanming State Key Lab. of Security Control and Simulation of Power Systems and Large Scale Generation Equipments Department of Electrical Engineering Tsinghua University Beijing100084 China

This study investigated the air-gap magnetic field distribution and inductance characteristics of a long primary sectional powered variable pole pitch linear induction motor (VPPLIM). A one-dimensional analytical model and a 2-D finite element model were used to analyze the air-gap magnetic field distribution in the VPPLIM with harmonic fields for uniformly accelerating the mover with a typical AC supply. The air-gap magnetic field distribution was used to develop analytical expressions for the self-and mutual-inductances of the motor and their characteristics. The analytical expressions are verified by the finite element simulations. ©, 2014, Press of Tsinghua University. All right reserved.

关键词： Inductance

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Transient stability assessment based on 2D combined attribute decision tree

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2009年第SUPPL. 1期29卷 17-24页

作者： Wang, Kang Sun, Hong-Bin Zhang, Bo-Ming Wu, Wen-Chuan Jiang, Wei-Yong State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Haidian District Beijing 100084 China

A method for the power syst.m transient stability assessment based on 2D combined attribute decision tree was proposed. Different from single attribute decision trees, the 2D trees combine two attributes as one automatically to improve its classifying ability in case of multi-dimension and nonlinear border among classes. In the proposed 2D tree, Gini coefficient based 2D combined splitting criterions was adopted and search method for splitting line in an inverse direction was developed. Case study was carried out in one-machine infinite bus syst.m, IEEE 39-bus syst.m and a real provincial syst.m. Results show that, 2D combined attribute decision trees generated by the proposed method are smaller in structure, have the higher accuracy and generalization ability than that generated by the single attribute decision trees. Meanwhile, some important relationship between physical variables in power syst.ms can be mined by the proposed method. Advantages mentioned above make that the proposed method is potential for real-life power syst.m applications. © 2009 Chin. Soc. for Elec. Eng.

关键词： Decision trees

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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 syst.m 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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Impedance fault location algorithm for UHV long transmission lines with single-line-to-ground faults

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Dianli Xitong Zidonghua/Automation of Electric power syst.ms 2008年第14期32卷 25-29页

作者： Wang, Bin Dong, Xinzhou Bo, Zhiqian Klimek, Andrew State Key Lab. of Control and Simulation of Power Systems and Generation Equipments Department of Electrical Engineering Tsinghua University Beijing 100084 China AREVA T and D Automation Co. Stafford ST17 4LX United Kingdom

Ultra-high-voltage (UHV) transmission lines (over 750 kV) normally have larger shunt capacitance and longer transmission radius, which impose limitations of direct application of traditional impedance algorithm. A novel impedance fault location algorithm is proposed for UHV transmission lines with single-line-to-ground faults due to higher voltage level than 750 kV. It is based on the precondition that the negative sequence current phase at meter location can precisely describe the phase information of negative current in fault path or fault voltage. The algorithm is immune to the influence of shunt capacitance with distributed parameters modeling for transmission line, and is not disturbed by fault resistance with fault location calculation at zero-crossing point of voltage at fault point. Theoretical analysis and simulation prove that the proposed method can guarantee good fault location accuracy, and fulfill the requirements in the field.

关键词： Electric lines

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