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Design optimization of ferrite rings for VFTO mitigation

IEEE Transactions on power Delivery 2014年第99期PP卷 1-1页

作者： He, Jiaxi Guan, Yonggang Liu, Weidong Chen, Weijiang Li, Zhibing Department of Electrical Engineering State Key Lab of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing100084 China State Grid Corporation of China Beijing100031 China China Electric Power Research Institute Beijing100192 China

Very-fast transient overvoltage (VFTO)-related problems are raising growing concerns in China with the development of ultra-high voltage. The practice of fitting ferrite rings on gas-insulated switchgear busbars for VFTO mitigation has long been proposed but few investigations on its design optimization were conducted. Based on theoretical analysis of the simplified model, the optimal damping condition of ferrite rings is proposed, which is conducive to the type selection. The number of rings to be employed to ensure visible suppressing effects is given through simulations and the influence of the saturation is discussed. Impact on the power frequency is analyzed to be negligible. Finally, comparisons aremade between the theoretical conclusions and existing experiment results, which approve the optimal damping condition and agree with the number of rings to be employed. © 2014 IEEE.

关键词： Electric switchgear

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Discussion on tower shunt coefficient of UHV DC transmission line under lightning stroke

Discussion on tower shunt coefficient of UHV DC transmission...

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International Conference on Lightning Protection (ICLP)

作者： S Chen J Hu B Zhang Y Yin M Hua State Key Lab of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing China China Electric Power Research Institute Beijing China Tibet Electric Power Research Institute Lhasa China

ISBN: (纸本)9781479935451

The development of UHV transmission technology brings longer transmission distance, higher towers and more complicated terrain along the transmission lines, which make the shunt performance of transmission line under lightning stroke more diversiform compared to conventional ones. This paper discusses the effects of factors, such as lightning current waveform, footing resistance, transmission line span etc., on the shunt coefficient of UHV DC transmission lines, which is of great significance for setting out lightning-proof measures as well as the location of lightning stroke point. It is referred that lightning current waveform especially its front time as well as tower footing resistance plays a significant role in determine of the tower shunt coefficient under lightning stroke. As the results indicates, the shunt coefficient of ground wire gets larger as the footing resistance increases while it decreases first and then increases as the front time of the lightning current waveform increases. The shunt coefficient of tower is just the opposite.

关键词： EMTDC Educational institutions Poles and towers Wires Wide area networks Lightning

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Simplified mathematical model of inter-turn short circuit of field windings in hydro-generators and its application

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Science China(Technological Sciences) 2013年第4期56卷 898-909页

作者： HAO LiangLiang WU JunYong SUN YuGuang WANG XiangHeng School of Electrical Engineering Beijing Jiaotong University State Key Lab of Control and Simulation of Power Systems and Generation Equipment Tsinghua University

Inter-turn short circuit of field windings is a common electrical fault of *** is an important method of investigating the fault and providing data support for fault ***,huge numbers of pole pairs and damper loops in large hydro-generators would lead to lengthy calculation time,hindering scientific research and engineering *** deal with this problem,we analyze a theoretical basis for a damper winding simplified model and then propose an equivalent treatment *** the analysis of steady-state current harmonic characteristics of generators with different stator winding configurations during the fault,the simplified models suitable for steady-state calculation are derived from two aspects,namely,additional rotor harmonic current frequency characteristics and the relationship of the amplitude as well as the phase of each branch current of the *** calculation and experimental results of the two simplified models are then compared to verify the models' correctness.A calculation example of the Three Gorges left bank VGS generator shows few deviations between the calculation results of the simplified model and the original ***,the calculation time using the simplified model is 1/1500 that using the original model,which provides a more effective tool for on-line fault ***,the sensitivity-verification application of the fault-monitoring scheme based on the stator steady-state unbalanced current RMS is *** result shows that the scheme can monitor two-turn short circuits of field windings in the Three Gorges generator and provide high sensitivity.

关键词： hydro-generator field windings inter-turn short circuit simplified model on-line monitoring

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

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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 system. Besides, the result of IEEE 30, 57, 118 test systems 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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Nanopowder production by gas-embedded electrical explosion of wire

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Chinese Physics B 2013年第4期22卷 350-353页

作者：邹晓兵毛志国王新新江伟华 State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Electrical Engineering Tsinghua University Department of Physics and Chemistry College of Science North China University of Technology

A small electrical explosion of wire （EEW） setup for nanopowder production is constructed. It consists of a low inductance capacitor bank of 2 μF–4 μF typically charged to 8 kV–30 kV, a triggered gas switch, and a production chamber housing the exploding wire load and ambient gas. With the EEW device, nanosize powders of titanium oxides, titanium nitrides, copper oxides, and zinc oxides are successfully synthesized. The average particle size of synthesized powders under different experimental conditions is in a range of 20nm–80nm. The pressure of ambient gas or wire vapor can strongly affect the average particle size. The lower the pressure, the smaller the particle size is. For wire material with relatively high resistivity, such as titanium, whose deposited energy Wd is often less than sublimation energy W s due to the flashover breakdown along the wire prematurely ending the Joule heating process, the synthesized particle size of titanium oxides or titanium nitrides increases with overheat coefficient k （k = W d /Ws ） increasing.

关键词： electrical explosion of wire nanosized powders particle size

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Interval economic dispatch model with uncertain wind power injection and spatial branch and bound method

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2014年第22期34卷 3707-3714页

作者： Ding, Tao Guo, Qinglai Bo, Rui Zhang, Liping Sun, Hongbin Wu, Wenchuan Zhang, Boming State Key Lab of Control and Simulation of Power Systems and Generation Equipment Department of Electrical Engineering Tsinghua University Haidian District Beijing100084 China Midwest ISO St. Pau55108 United States Department of Mathematical Science Tsinghua University Haidian District Beijing100084 China

power injection becomes stochastic due to large-scale wind power integration into power grid, which greatly challenges the traditional power grid. If the uncertainty is modelled using the interval number, the solution of economic dispatch model can also be represented as an interval number. To achieve the precise upper and lower bound, two deterministic programming models were deduced: the optimistic solution can be obtained by an optimistic model using linear programming, whereas the pessimistic solution achieved by a pessimistic model is an NP-hard problem, which can be transformed into a bilinear programming by duality theory. Then a linear relaxation technology, spatial branch and bound method were used to obtain the global pessimistic solution. Therefore, the interval bound information can provide the operator with institutive bound information for the future security assessment. Finally, a test system with 15 generators and 300 nodes was studied at different time scales. The result, compared with interior point method and enumeration, shows the effectiveness of proposed method. © 2014 Chinese Society for Electrical Engineering.

关键词： Wind power

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Solving of interval DC power flow using interval Hull algorithm with preconditioning

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Dianli Xitong Zidonghua/Automation of Electric power systems 2014年第3期38卷 130-136页

作者： Ding, Tao Guo, Qinglai Bo, Rui Gu, Wei Sun, Hongbin Zhang, Boming Department of Electrical Engineering Tsinghua University Beijing 100084 China State Key Laboratory of Control and Simulation of Power Systems and Generation Equipments Tsinghua University Beijing 100084 China Midwest Independent Transmission System Operator Inc. Saint Paul 55108 United States School of Electrical Engineering Southeast University Nanjing 210096 China

With intermittent sources integrated into the power grid, power flows of the power grid are getting stochastic. Considering the uncertainty problem of DC power flow in the high voltage transmission system, this paper recommends an interval Hull algorithm with preconditioning to solve the interval DC power flow. Firstly, the diagonal dominant interval coefficient matrix is formed by preconditioning, then the H-matrix is obtained using the interval Hull algorithm. Different approximation methods are employed for the comparison matrix of H-matrix to improve precision. And the upper and lower bound of the distribution of interval DC power flow is obtained with the iterative method. The interval Hull algorithm and Monte Carlo algorithm are compared in the 9-bus test system, the result of which shows that the uncertainty in grid parameters is the main cause of errors. Furthermore, the Hull algorithm with preconditioning, the interval Hull method, the Krawczyk operator iteration method and the Gauss elimination method are compared in terms of accuracy and computing time on an IEEE 57-bus and an IEEE 118-bus test system, respectively. It is shown that the Hull method with preconditioning has the best accuracy, and the time complexity is far lower than that of the Monte Carlo algorithm. © 2014 state Grid Electric power Research Institute Press.

关键词： Iterative methods

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Modeling and analysis of unit commitment considering RCAES system

Modeling and analysis of unit commitment considering RCAES s...

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Chinese control Conference (CCC)

作者： Bin Liu Laijun Chen Yu Zhang Chen Fang Shengwei Mei Yuan Zhou State Key Lab of Control and Simulation of Power Systems and Generation Equipment Tsinghua University Beijing Beijing CN Electric Power Research Institute State Grid Shanghai Municipal Electric Power Company China Key Laboratory of Cryogenics Technical Institute of Physics and Chemistry Chinese Academy of Sciences Beijing CN

Regenerative compressed air energy storage (RCAES) system is a practical and efficient solution to large-scale integration of renewable energy problems faced by power systems currently. Appropriately modeling of RCAES system is critical to its practical application, whereas research in this area has been very limited. According to the energy storage and transformation process, a concise model of RCAES system applicable to power scheduling field is proposed. Then, a unit commitment model with RCAES system is formulated as a MILP problem which can be accurately solved with high computation efficiency by CPLEX. A modified IEEE 39 bus system is used to study the impacts of parameters of RCAES system on unit commitment and the effectiveness of the proposed model is then validated. Furthermore, the proposed model can also be employed to optimize key parameters of RCAES system, e.g. efficiency and capacity of each part in an integrated way.

关键词： Energy storage Heating Computational modeling Wind power generation power grids Schedules

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Identification of inactive constraints for SCED model considering uncertain power injection

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Zhongguo Dianji Gongcheng Xuebao/Proceedings of the Chinese Society of Electrical Engineering 2014年第34期34卷 6050-6057页

作者： Ding, Tao Bo, Rui Guo, Qinglai Sun, Hongbin Huang, Can Li, Fangxing State Key Lab of Control and Simulation of Power Systems and Generation Equipments Dept. of Electrical Engineering Tsinghua University Haidian District Beijing100084 China Midwest ISO St. Paul MN55108 United States Department of Electrical Engineering and Computer Science The University of Tennessee Knoxville TN37996 United States

With the constant expansion of power grid, a large number of security constraints have put tremendous challenges to the online economic dispatch. An efficient tool to eliminate the inactive constraints becomes necessary for security constraints economic dispatch (SCED) in large power systems. In this paper, considering the uncertainty of renewable energy integration, a fast and effective method to identify the inactive security constraints was proposed. Firstly, the definition of uncertain inactive security constraints and a necessary and sufficient condition to identify those were presented respectively. Considering the time-consuming identification, we relaxed the feasible region of original SCED model and utilized greedy algorithm to quickly eliminate part of inactive constraints. Then another necessary and sufficient condition was proposed and verified, where the remaining inactive constraints could be identified. Through the simulation of 24-time periods 9-bus system and 96-time periods IEEE 118-bus system, the speed and effectiveness of proposed method were verified. Moreover, the results can help dispatch operators to locate the transmission lines with the highest congestion risk. © 2014 Chin. Soc. for Elec. Eng.

关键词： Scheduling

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Design of grid-connected directly driven wave power generation system with optimal control of output power

Design of grid-connected directly driven wave power generati...

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2013 15th European Conference on power Electronics and Applications, EPE 2013

作者： Qing, Kang Xi, Xiao Zanxiang, Nie Lipei, Huang Kai, Sun State Key Lab of Control and Simulation of Power System and Generation Department of Electrical Engineering Tsinghua University Haidian District Beijing China

ISBN: (纸本)9781479901166

This paper presents a directly driven wave power generation system which is connected to power grid composed of permanent magnetic linear generator(PMLG), generator side converter, grid side converter, controller and grid. control strategies based on back to back converter structure was proposed: vector decoupling control was used to generator side converter aiming at optimize power extraction from wave energy;Grid voltage oriented control was used to grid side converter in order to make the current sinusoidal and realize unit power factor control. Since the DC link voltage has fluctuation using traditional method, a method with power feed forward was proposed to keep the DC link voltage stable and improve the dynamic response of the system. A simulation model was built for the whole system in Matlab/Simulink and simulation results verified that the proposed control strategy is feasible and effective. © 2013 IEEE.

关键词： Simulink

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