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IEEE power and Energy Society General Meeting

作者： Bo Jiang Xinzhou Dong Shenxing Shi Bin Wang State Key Lab. Of Control and Simulation of Power System and Generation Equipment Dept. of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781467380416

Single Line to Ground (SLG) faults in non-effectively grounded networks are difficult to detect. Immune to neutral point grounding type, load conditions and system operation conditions, traveling-wave based method is an effective fault line identification method. However, due to the strong coupling between the double-circuit lines, the wavefront magnitude of them are the same, and the polarity of them are opposite. Thus, the mal-identification will be resulted under such condition. This paper analyzed the traveling wave characteristics of double-circuit lines, and proposed an improved fault line identification method based on the initial process of zero sequence currents and voltage traveling waves. Tests show that, the proposed method has high effectiveness in fault line identification of double-circuit lines in distribution networks.

关键词： distribution networks double-circuit fault line identification non-effectively grounded traveling wave Double circuit power grids line down Earth faults traveling waves single line

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Dynamic Response of Rubbing Happening in a Flexible Rotor-Bearing system

Dynamic Response of Rubbing Happening in a Flexible Rotor-Be...

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2015 International Conference on Electrical, Automation and Mechanical Engineering(EAME 2015)

作者： J.M.Chen D.X.Jiang T.T.Deng J.S.Wang J.L.Zhong S.B.Wang State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal Engineering Tsinghua University Guizhou Electric Power Research Institute

ISBN: (纸本)9781510806528

To reduce the steam loss and raise the efficiency of the steam turbine,the vapour seals are applied in the inner cylinder of the steam *** small gap may easily results in the rubbing happening in the inner ***,the rotor is a flexible *** this paper,dynamic response of rubbing happening in a flexible rotor-bearing system was studied.A simplified flexible rotor-bearing system was constructed,whose rotating speed was between the 1st and 2nd critical rotating *** effect was considered in the analysis,*** rubbing introduce heat and result in the thermally induced *** transient thermal bow was treated as a pair of moments functioning on the shaft segment where rubbing *** shows the amplitude and phase of vibration would be stable after a long *** severity of rubbing affect the stabilization time,which could be regarded as a diagnostic feature to identify the severity of rub happening in a flexible rotor-bearing system.

关键词： thermally induced vibration equivalent thermal moment stabilization time rubbing flexible rotor-bearing system

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Ambient signal based load model parameter identification using optimization method

Ambient signal based load model parameter identification usi...

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IEEE General Meeting power& Energy Society

作者： Xinran Zhang Chao Lu Yingduo Han Songtai Yu Jifeng Wang He Huang Yinsheng Su State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing China China Southern Power Grid Guangzhou China

Load modelling is a crucial part in modelling a power system. The complex, nonlinear and stochastic characteristics of power load increase the difficulty of modelling. In this paper, a new approach of ambient signal based load model parameter identification method is proposed to solve this problem. With the proposed method, load model parameter can be identified in any time regardless of the existence of fault. First, Z+M model is simplified to reduce the number of parameters to be identified. Then, parameters of Z+M model are identified with an optimization method, the objective function of which is calculated from WAMS measured power and voltage data. An iterative process is proposed to solve the problem of initial value sensitivity in optimization problems. Finally, the effectiveness of this identification method is validated through the simulation results on WSCC three machines nine nodes system under different operation situation including both small disturbance and large disturbance.

关键词： Load modeling Optimization Integrated circuit modeling Parameter estimation Data models Reactive power power measurement

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Research on perception of power system state based on WAMS

Research on perception of power system state based on WAMS

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Innovative Smart Grid Technologies (ISGT)

作者： Yunfeng Cheng Chao Lu Kun Men Liang Tu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing P.R. China Academy of China Southern Power Grid Guangzhou P.R. China

ISBN: (纸本)9781479917860

The development of Smart Grid requires more accurate and fast for perception, assessment and control of power system state. Widely installed phasor measurement units (PMU) and mass PMU measurements provide a good foundation for this requirement, because PMU can directly measure bus voltage phasors at the rate of tens of milliseconds. Thus, the number of PMU installed in the power grid and the reliability and accuracy of PMU measurements are of great importance, which directly affect the feasibility and reliability of state perception. Actually, PMU measurements may contain bad data and the accuracy of phase measurements is not high enough. Estimation method is an effective way to deal with data contaminated by noise and bias. In this paper, we proposes the complex number weighted least squares (CWLS) estimation algorithm to process PMU measurements directly in the complex domain to obtain more accurate system state. Phasor error characteristics in the complex domain are analyzed depth which shows the proposed algorithm is robust to phase error. Meanwhile, an effective bad data identification method is proposed. Test results demonstrate the performance of the CWLS algorithm from the perspectives of computional efficiency, estimation quality and adaptability to inconsistent measurment errors, the robustness of the CWLS algorithm and the effectiveness of the proposed bad data identification method is also shown in the tests.

关键词： Phasor measurement units Estimation Measurement errors Voltage measurement power systems Phase measurement Algorithm design and analysis

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Natural Frequency and Dynamic Response of Rotor system of Steam Turbine Modelled with Euler-Bernoulli Beam

Natural Frequency and Dynamic Response of Rotor System of St...

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2015 International power,Electronics and Materials Engineering Conference(IPEMEC 2015)

作者： T.T.Deng J.S.Wang X.J.Li J.L.Zhong S.B.Wang S.P.An W.G.Yang D.X.Jiang Guizhou Electric Power Test and Research Institute State Key Laboratory of Control and Simulation of Power System and Generation Equipments Department of Thermal EngineeringTsinghua University

ISBN: (纸本)9781510806474

Based on Finite element method(FEM),analysis of natural frequency and dynamics response is carried out in this ***,modeling of rotor system in steam turbines is analyzed with Euler-Bernoulli beam ***,natural frequency of the rotor system is obtained and ***,dynamic response of the rotor system is simulated and the vibration of the rotor system is *** results show that the proposed model can obtain results with high accuracy,and the model is *** modeling approach presented in this work provides a fast and accurate method in analyzing dynamic characteristics of the practical rotor system in steam turbine units

关键词： Natural frequency transient response rotor system steam turbine Euler-Bernoulli Beam

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A real-time wind power control method for power systems with high wind power penetration and its implementation

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Dianli Xitong Zidonghua/Automation of Electric power systems 2015年第21期39卷 23-29页

作者： Wang, Bin Sun, Yong Wu, Wenchuan Zheng, Taiyi Zhang, Boming State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing100084 China Department of Electrical Engineering Tsinghua University Beijing100084 China State Grid Jilin Electric Power Supply Company Changchun130021 China

A real-time wind power control method is proposed to accommodate the severe fluctuation of wind power, which can be used in power systems with high wind power penetration. The maximum allowable wind power generation is estimated online according to the automatic generation control (AGC) downward spinning reserve and the tie-line power deviation. Considering the different priorities for wind farms and the transmission security constraints, different control strategies, such as corrective control to eliminate the transmission congestion, optimal dispatch considering the trade-off between minimum curtailment of wind power and the fairness among wind farms, are integrated in the proposed method. The numerical simulation on the test system and the results of field operation in a provincial power grid show that the method is efficient and practical. © 2015 Automation of Electric power systems Press.

关键词： Wind farm

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A hybrid converter for energy management of EV drives

A hybrid converter for energy management of EV drives

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

作者： Teng Hu Lie Xu Lin Qiu Yongdong Li Xuejun Han Department of Electrical Engineering Northeast Dianli University Jilin China State Key Lab. of Control and Simulation of Power System and Generation Equipment Tsinghua University Beijing China

This paper proposed a novel hybrid power converter topology based on cascaded H-bridge (CHB) and matrix converter (MC) in order to improve the performance of the conventional energy management systems in EV/PHEV application. The power demand by the load is supplied by the generator and batteries, which are connected to the primary winding of the medium frequency transformer (MFT) by the matrix converter and the cascaded H-bridge respectively. The power transfer between the sources and load can be controlled and isolated by using the MFT. The cascaded H-bridge, as the energy control unit, can be used to balance the voltage/SOC of battery packages individually, significantly improve the modularity, stability and safety of EV system.

关键词： Batteries Matrix converters Energy management system-on-chip Topology Voltage control Windings

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Automatic voltage control of wind farms based on model predictive control theory

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Dianli Xitong Zidonghua/Automation of Electric power systems 2015年第7期39卷 59-67页

作者： Xu, Fengda Guo, Qinglai Sun, Hongbin Lan, Haibo Liu, Haitao Liu, Xiaomin Department of Electrical Engineering Tsinghua University Beijing100084 China State Key Laboratory of Control and Simulation of Power System and Generation Equipments Tsinghua University Beijing100084 China State Grid North Hebei Grid Company Limited Beijing100053 China

Voltage fluctuations occur frequently in wind farms as a result of wind power perturbation, while reactive power control of various devices is always uncoordinated and often has a time lag when the system operates in the traditional control mode that only uses the current data for decision-making. In this case, a method for coordinated control of the reactive power of wind turbine generators (WTGs) and static var generators is proposed based on model predictive control (MPC). Unlike the traditional voltage control method, the control method proposed has the realization of optimization of the voltage control curve and the dynamic process of reactive power regulation in the future window of time as its objective. An auto regression moving average (ARMA) model is used to predict the active power of WTGs while the reactive power of WTGs and the SVG is forecasted using a first-order inertia link and a proportional integral (PI) link, respectively. Voltages in the wind farm are solved with the help of a sensitivity matrix. Thus an optimization model is developed for both the minimization of PCC voltage deviation and the maximization of SVG reactive power reservation in a future window of time. The optimizing model is solved using CPLEX tools with the dual simplex algorithm. In order to test the performance of the MPC controller, multiple cases with different wind circumstances are simulated on a DIgSILENT platform. simulation results reveal that by predicting the states of various instruments in wind farms during a period of time in the future, the proposed control method is able to rationally arrange fast/slow reactive power to respond to predictable changes of the system in advance and keep voltage stable. ©2015 State Grid Electric power Research Institute Press

关键词： Reactive power

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Reducing the impact of source internal resistance by source coil in resonant wireless power transfer

Reducing the impact of source internal resistance by source ...

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作者： Zhang, Yiming Lu, Ting Zhao, Zhengming State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing China

ISBN: (纸本)9781479956982

Wireless power transfer (WPT) is the state-of-the-art research interest. In the WPT system efficiency is an important figure of merit. In order to reduce the impact of the source internal resistance and improve the system efficiency of the conventional two-coil structure, a source coil is added to the two-coil structure, forming a three-coil structure. Both the two-coil structure and the three-coil structure are modeled and analyzed with the circuit theory. The system efficiencies of both structures with optimal loads and a fixed load are deduced. The system efficiency of the three-coil structure is proved to be higher than that of the two-coil structure. An experimental apparatus is implemented and the experimental results match well with the theoretical calculations. The larger the source internal resistance, the more significantly the addition of the source coil improves the system efficiency. © 2014 IEEE.

关键词： Energy transfer

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Electrical properties of oil-paper insulation affected by water conductivity during paper-making process

Electrical properties of oil-paper insulation affected by wa...

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32nd Electrical Insulation Conference, EIC 2014

作者： Huang, Jianwen Zhou, Yuanxiang Jin, Fubao Sha, Yanchao Zhang, Ling Le, Trung Hieu State Key Laboratory of Control and Simulation of Power System and Generation Equipment Department of Electrical Engineering Tsinghua University Beijing 100084 China

ISBN: (纸本)9781479927876

Developments of ultra-high voltage grid in China require better insulation materials, and that forces the transformer presspaper and pressboard manufactures to pay more attention to the papermaking process to enhance their product qualities. In this study, pure water and three kinds of sodium chloride solutions with conductivities of 100 μS/cm, 500 μS/cm and 1000 μS/cm were respectively used to prepare presspaper samples. By vacuum impregnation, four kinds of oil-paper samples were acquired. Test results showed that relative permittivity and tand of oil-paper specimens first varied little then increased a lot with the increasing of water conductivity;DC breakdown field decreased while AC breakdown field changed little. To confirm the differences were due to water conductivity, ion chromatography was used to determine the sodium and chloride ion contents of the presspaper samples, we found that the ion contents increased with electrical conductivity. This indicates that water conductivity does have effects on most electrical properties of oil-paper insulation and lower conductivity can bring better insulation performances. © 2014 IEEE.

关键词： Ion chromatography

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